A thermosensitive recording material is a recording material having a structure where an under layer, a thermosensitive recording layer, which colors upon application of heat, and a protective layer are formed on a support. As for application of heat to color the thermosensitive recording material, a thermal printer equipped with a thermal head therein is used.
A thermosensitive recording method using the thermosensitive recording material is advantageous over other recording methods, because it is not necessary to perform developing or fixing, recording can be performed within a short period of time using a relatively simple device, and a cost thereof is low. Therefore, the thermosensitive recording method using the thermosensitive recording material has been used in various fields, such as POS (e.g., for fresh food, lunch boxy, ready made food), copying (e.g., for books, and documents), telecommunication (e.g., facsimile), ticketing (e.g., a ticketing machine, a bill, and a receipt), and a tag for packaging for air crafts.
As for a support of the thermosensitive recording material, synthetic paper or a synthetic resin film has been used, as they have excellent size stability and physical strength, and are insoluble to water (see PTL 1 and PTL 2).
However, a coating liquid cannot be penetrated into a film base, such as the synthetic paper, and the synthetic resin film, compared to the degree of the penetration thereof to paper base. Therefore, adhesion between the support and the under layer, adhesion between the under layer and the thermosensitive recording layer, and adhesion between the thermosensitive recording layer and the protective layer become weak. Especially, the adhesion between the support and the under layer tends to weaken.
In the case where a thermosensitive recording material is stored in a freezing environment in a state where a surface of the thermosensitive recording material is in contact with a plastic container with the thermosensitive recording material being peeled due to the aforementioned reduction in adhesion, or separated due to elusion of water-soluble components especially as being wet with water, or wet with water or condensation water, the surface of thermosensitive recording material is strongly adhered to the plastic container via ice. If the plastic container is released from the thermosensitive recording material with force, there is a problem that the surface of the thermosensitive recording material is peeled. As a result, as illustrated in FIG. 1, the thermosensitive recording layer of the thermosensitive recording material is peeled, and therefore it may become difficult to visually confirm the recorded information, or a problem, such as a reading failure with a barcode reader, may occur.
Note that, in the present invention, the freezing environment means an environment of −20° C.
Accordingly, there is a need for a thermosensitive recording material having high coloring sensitivity and high image density without causing peeling of a thermosensitive recording layer even upon application of mechanical external force in a freezing environment.